The present invention relates to a cassette reading processing device by which the reading processing of the image information is conducted on a cassette in which an accumulative phosphor appropriate for the radiation photography accommodated, a cassette reading processing method and a cassette.
Conventionally, a cassette in which a radiation image photography is conducted on the cassette in which the accumulative phosphor is accommodated, and from the accumulative phosphor after the photographing, the radiation image is read, is used for the medical care refer the following Patent Documents 1 to 6). In such a conventional cassette, as the accumulative phosphor, for example, powder imaging plate BaFI phosphor is used.
As a cassette structure using the powder imaging plate (BaFI) phosphor, as shown in the following, various methods are put in practical use. In the following Patent Document 1, a part of the cassette leading edge part is opened, and a method in which a flexible recording medium is taken out by a suction cup, is adopted. In the following Patent Document 2, in the same cassette structure as the above Patent Document 1, a method in which a recording medium whose rigidity is assumed to be high, is conveyed by a roller, is adopted. In the following Patent Document 3, a method in which a front plate is entirely opened around a hinge, is adopted.
Further, in the following Patent Document 4, a detachable type cap and the recording medium whose rigidity is comparatively high are integrated, and a structure in which the recording medium is taken in and out to the cassette main body, is adopted. In the following Patent Document 5, a structure in which the front plate and the back plate are perfectly separated, and the combination of both is conducted by the opening and closing of a mechanical lock means, is adopted. In the following Patent Document 5, a structure in which the front plate and the back plate are perfectly separated, and the combination of both is conducted by an attraction force of the magnet and the separation of both is conducted by the deflection, is adopted.
The powder imaging plate phosphor is not a big problem from the view point of the maintenance of the image quality or durability (deterioration of the image quality), even when any structure of the various cassette structures as described above, is adopted.
Further, in the cassette of the following Patent Document 2, there is an description that a non-woven fabric as the cushioning material is pasted on the plate section opposite to the image recording layer of the radiation image recording medium, and because the non-woven fabric is not frayed, there is no case where it becomes a dust and an image defect is caused, however, in practice, there is a possibility that, when the recording medium is inserted into the cassette, the non-woven fabric is cut by an edge of the recording medium and dusts are generated, and there is a problem that, depending on the repeated use, dusts are generated, and the image defects are produced.
On the one hand, recently, to the powder imaging plate phosphor, the phosphor is remarked from the view point that the phosphor in which a needle imaging plate is grown to a predetermined thickness by the deposition method (deposition method), can obtain the high sensitivity. In the needle imaging plate by the deposition method, the present inventors and so on find a fact that, when the film thickness is a thin film of nm (nano-micron) level, the strength of the phosphor is equal to that of the powder imaging plate (coating type) one, however, for the purpose that the phosphor having an advantage of the high sensitivity is put into a practical use to the CR system, a certain degree of film thickness is necessary, and when the needle imaging plate (column crystal) by the deposition method (vapor phase growing-up method) becomes thick, it becomes fragile, and a damage is easily subjected by the external force. Accordingly, it is not preferable that the external force is added to the recording medium, it is deformed or the impact force is received, while it is transferred or at the time of operation of photographing, and it is also not preferable that, when the photographing is completed and the recording medium is taken from the cassette, and after reading of the image information is completed, it is inserted (into the cassette) again, the impact force is given to the recording medium.
For example, there is a case where, for an inspection and photographing in the hospital, a patient on a bookie-table or a bed is radiation-photographed, and in this case, under a condition that the patient lies down on a comparatively soft material such as bedclothes which are not rigid, because the cassette is inserted between this soft material and the patient, at the time of photographing, the cassette is going to be 3-dimensionally deformed by the body weight of the patient, and after the photographing is completed and when the load onto the cassette is released, the cassette is going to return to the original. Every time when the photographing is repeated, the above-described movement is repeated. Further, even when the cassette is put on a comparatively rigid table, there is a case where the front plate is deflected by the load of the patient applied on the front plate, and an external force is given to the recording medium surface in the cassette, and it is an important problem for the recording medium formed of the needle imaging plate by the deposition method as described above.    (Patent Document 1) Tokkai 2000-275763    (Patent Document 2) Tokkaihei 05-313267    (Patent Document 3) Tokkaihei 07-120854    (Patent Document 4) Tokkaihei 11-271895    (Patent Document 5) Tokkai 2002-156716    (patent Document 6) U.S. Pat. No. 4,961,000